1. Field of the Invention
The present invention relates to an automotive sound-proof material and a damping material therefore, and is concerned with improvements in or relating to the performance and working properties of such a sound-proof material and a method for the production thereof.
2. Statement of the Prior Art
Heretofore, a sound-proof material has been attached to an automotive dash portion for sound-absorption and -insulation purposes to prevent the entrance of noises from an engine compartment.
A sound-proof material obtained by integrating together a sound-absorption material such as felt and a sound-insulating surface material or by laminating an additional asphalt sheet on the sound-absorption material is used as a sound-proof material for dash, and is applied in such a manner that the sound-absorption material such as felt or the asphalt sheet comes in contact with a dash panel. For instance, Japanese Utility Model Laid-Open Publication No. 59-39248 discloses a sound-proof material formed of a plywood-like three-layer formed silencer comprising a sound-absorption material interposed between and laminated onto a viscous foamed material such as an asphalt foam material and a surface material such as PVC with the use of a bonding agent, said viscous foamed material being closely attached to a dash panel. Japanese Utility Model Laid-Open Publication No. 62-103755 discloses another sound-proof material comprising an asphalt foam material, a sheet formed of PVC, etc., a sound-proof material such as felt and a sheet formed of PVC, etc.
However, it is now desired to achieve further reductions of noises generated in a car engine compartment and so there is an urgent need to provide a sound-proof material having a more improved sound-proof effect at 40.degree. to 60.degree. C., especially while a car is running. From this point-of-view, although the sound-proof material of the structure comprising the asphalt sheet/sound absorption material/surface material is superior to that of a structure including no asphalt sheet, it still fails to produce such a sound-proof effect as now desired.
In order to attach such a sound-proof material using an asphalt sheet to a dashboard, the asphalt sheet is thermally fused to the dashboard on the coating and baking line for automotive bodies and an integral member of a sound-proof material and a surface material is attached to the asphalt sheet. A problem with this sound-proof material is that when it is intended to attach to the dashboard the asphalt sheet (of the integral member of the asphalt sheet/sound-proof material/surface material previously prepared), there is no choice but to use two steps, one step of thermally fusing the asphalt sheet to the dashboard and the other step of attaching an integral member of the sound-absorption material/surface material to the asphalt sheet, due to the thermal deformation of the sound-absorption and sound-insulating materials or other disadvantages.